Welding is a fabrication or process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the substrates of the work-piece and adding a filler material to form a pool of molten material, a.k.a., the weld pool, at the substrate interface. After the weld pool at the substrate interface cools, a high strength joint is produced.
Depending on the type and quality of the materials sought to be joined, the same welding process may expend/consume vastly different amounts of energy to generate a robust weld. Additionally, a welding process that expends more energy may require larger, heavier, more powerful, and thus more expensive welding equipment. Such increased consumption of welding energy tends to reduce the overall efficiency of the welding operation, and, coupled with the higher cost and size of the welding equipment, tends to increase the effective cost of the finished assembly.
Some welding processes involve melting the base material microstructure at the weld interface, while others are configured as solid-state joining processes. One type of a solid-state joining process is friction-stir welding (FSW). FSW is frequently used for joining aluminum components, because, in comparison with alternative welding processes, FSW inputs smaller amounts of thermal energy and generates less thermal distortion in the components being joined.